The present invention relates to apparatus for the circumferential irradiation of objects, especially of vessels, hollow organs and solid tissue by means of high-intensity optical radiation which is conducted via a flexible optical fiber.
Such apparatus is in use in medical practice and is described, for instance, in "Laser in Surgery and Medicine" 6, pages 150-154 (1986) as well as in European Patent EP No. 01 52 766; high-intensity of the optical radiation is mentioned if the latter does not serve for illumination purposes but for coagulation or removal of tissue. In the first publication mentioned, the circumferential radiation of laser light is brought about by the provision that a cylindrical glass cap extending the fiber is placed inside out over the distant end; the inside wall of the latter is coated with a white synthetic material and its outside wall is roughened by sand blasting. By these measures, the greatest possible light scattering of the laser light emanating from the end of the fiber substantially axially is brought about, so that a diffuse radial radiation in the vicinity of the cap is accomplished. The apparatus described in the above-mentioned European Patent EP No. 01 52 766 differs, in contrast, in that the use of a cap is dispensed with and instead, the distant end of the optical fiber is freed of the jacketing. Also thereby, an essentially diffuse radial radiation of the laser light is to be achieved.
It is a disadvantage of the above-mentioned apparatus that the intensity is reduced substantially by the diffuse radiation, so that the coupled-in radiation power must be increased suitably for coagulation purposes or for removing tissue, stenoses and the like. This, however, also causes an increasing temperature rise of the cap and the distant end of the optical fiber. In addition, it is not possible with the known apparatus to bring, within a hollow organ with a diameter distinctly larger than that of the cap or the optical fiber, the laser radiation directed on small areas of the inside wall.